Cover for a radar sensor for motor vehicles

ABSTRACT

A cover for a radar sensor for motor vehicles, which has a wall provided with a three-dimensional relief structure, in which the wall including the relief structure is made of deep-drawn glass.

FIELD OF THE INVENTION

The present invention relates to a cover for a radar sensor for motorvehicles, which has a wall that includes a three-dimensional reliefstructure.

BACKGROUND INFORMATION

For example, radar sensors in motor vehicles are used for locatingvehicles driving ahead, so that automatic vehicle-to-vehicle ranging ispossible. It is desirable to integrate the radar sensor and its coverinto the radiator grille and, for example, to place it centrally in theupper region of the radiator grille, so that it has an excellent fieldof vision and is largely protected from damage by falling stones or thelike. It seems also useful that the relief structure of the covercarries the company insignia of the motor vehicle manufacturer.

The cover then has to satisfy a multitude of technical requirements. Forone, it must be transparent to radar and should interfere as little aspossible with the transmission of the radar waves and also create aminimum of interfering reflections. The company insignia of the motorvehicle manufacturer often includes very shiny surface components andshould therefore be effectively protected from environmental influences,so that this surface will not dull and lose its appearance. The outersurface of the radar sensor should be as robust as possible and, inparticular, not scratch easily.

A cover of this type is discussed in publication DE 103 38 506.4;however, the production of this cover is very complex and involves amultitude of method steps, so that it is relatively expensive and therisk of faults in the production process is fairly high.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a cover having athree-dimensional relief structure for radar sensors, which can beproduced cost-effectively and still is of high optical, radar-opticaland mechanical quality.

According to the present invention, this object is achieved in that atleast one layer of the wall provided with the relief structure is madeof deep-drawn glass.

Different glass manufacturers offer flexible glass plates, which aredeformable by deep-drawing, for instance. One example is a borosilicateglass that is distributed by the Corning company under the “WillowGlass” designation.

According to the present invention, this glass is reshaped bydeep-drawing such that it forms the three-dimensional relief structureof the cover. The glass composition can be selected so as to achievehigh transparency for radar waves, whose frequency typically lies on theorder of magnitude of approximately 77 GHz.

The use of the reshaped glass as base substrate for the cover allowshigh mechanical stability and robustness as well as high optical qualitywhile enabling a simultaneously cost-effective production. Numerouserror sources are omitted since fewer method steps are required than inconventional methods, so that the rejected material and thus thecomponent costs are minimized.

Advantageous embodiments and further refinements of the presentinvention are outlined in the dependent claims.

The appearance of the cover is able to be influenced by imprinting atleast portions of the relief structure made from glass and/or ametallization. The imprinted or metallized surfaces may be on the rearside of the cover facing the radar sensor, so that they are protectedfrom environmental influences. Furthermore, a plastic layer can beapplied onto the rear side of the metal layer by back-injection moldingor injection embossing, which forms a stable and distortion-freecomposite component together with the glass layer. The injection orinjection-embossing method makes it possible to achieve an excellentsurface abutment between the glass substrate and the plastic mass, sothat no air inclusions occur at which the radar waves would bereflected. At the same time, the plastic mass may be shaped in such away that it forms support elements for fastening the cover or the entireradar sensor to the radiator grille or to other body shell components ofthe motor vehicle.

A transparent casting compound or seal of plastic also may be providedon the front side of the cover, which compensates for unevenness of therelief structure, so that a smooth surface is obtained which can then beprovided with a scratchproof enamel, e.g., a duroplastic lacquer.Optionally, the depressions of the relief structure on the front sidemay also be filled by an uninterrupted transparent duroplastic resinlayer.

An exemplary embodiment is explained below with the aid of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a schematic section through a device for deep-drawing atransparent glass sheet.

FIG. 2 the device as recited in claim 1, at the end of a deep-drawingstep.

FIG. 3 an enlarged section through a part of the deep-drawn glass sheetin the tool according to FIG. 2.

FIG. 4 a section, analogous to FIG. 3, through the glass sheet followingadditional processing steps.

FIG. 5 a schematic section through a device for injection-embossing aplastic layer on the rear side of the glass sheet.

FIG. 6 a section through a device for applying a casting compound to afront side of the glass sheet.

FIG. 7 a section through a finished cover for a radar sensor.

FIG. 8 a front view of the cover according to FIG. 7.

DETAILED DESCRIPTION

According to FIG. 1, the starting material for producing a cover for amotor vehicle radar sensor is a flexible glass sheet 10, which is drawnoff a coil 12 in the form of an endless strip and passes between anupper tool 14 and a lower tool 16 of a punching and deep-drawing device18. Upper tool 14 has a circumferential punching die 20, with the aid ofwhich a circular blank, for example, is punched out of strip 10. Theblanking waste is then wound onto a coil 22 again on the other side ofdevice 18.

On the underside, upper tool 14 has a system of projections 24, whilelower tool 16 has a complementary system of depressions 26. When uppertool 14 is lowered, a blank 28 is punched out and deep-drawn byprojections 24 and depressions 26, and reshaped in such a way that athree-dimensional relief structure 30 is obtained.

Upper and lower tools 14, 16 are retained in exchangeable fashion in amachine bed 34 of device 18, so that covers that have different reliefstructures are able to be produced, which, for example, represent thecompany insignia of the individual motor vehicle manufacturer.

As FIG. 3 illustrates, the surfaces of upper tool 14 and lower tool 16facing the blank have coatings 36 made of PTFE (Teflon). Thisfacilitates the deep-drawing operation. The edges of depressions 26 inlower tool 16 are rounded, so that no ugly marks are produced on theside of the blank that later forms the outside of the cover.

When upper tool 14 is lifted up, deep-drawn blank 28 is ejected orpossibly transferred together with lower tool 16 serving as workpiecesupport to an imprinting station (not shown here), where the raisedparts of relief structure 32 are imprinted using a color enamel on therear side facing the radar sensor of the subsequent cover (the top sidein FIGS. 2 and 3), for instance in a pad printing process. One part ofenamel layer 38 formed in this manner is illustrated in FIG. 4.

In a further step, an opaque uninterrupted metallization layer 40 isapplied to the entire rear side (top side) of blank 28, which, forexample, has a thickness of at least 50 nm and may be made of indium,gold or tin, for reasons of radar transparency.

For a subsequent processing step, the imprinted and metal-coated blank28 is transferred to an injection-molding machine 42 having an embossingfunctionality, which is shown in FIG. 5 in a sectional view. In thisstep blank 28 may optionally also remain on lower tool 16 of thestamping and deep-drawing device serving as workpiece support, whereuponthe injection-molding device is repositioned and suitably positionedwith ejectors 44 in a bed 46 of the injection-molding device. Heatingducts 52 run through bed 46, a circumferential wall 48 as well as anembossing stamp 50 of the injection-molding machine, so that theinjection-molding machine together with blank 28 are able to be heatedto a temperature of 120 to 140° C., for example.

Circumferential wall 48 and embossing stamp 50 form the boundary of amold cavity 54 above blank 28, into which a preheated plastic melt isinjected via a sprue 56, which may be at a pressure of less than 500MPa. The plastic, for example, may be a polycarbonate or a duroplasticresin material.

Punch 50 is set apart from the circumferential wall of injection-moldingmachine 42 by a punch gap 58 and drives deeper into the mold cavityduring the injection-molding operation, so that the plastic melt isfirmly pressed against the metallization layer of blank 28. Thisachieves a full-surface adhesion of the plastic to the metallizationlayer of the blank without air inclusions. The adhesion can be improvedfurther by subjecting metallization layer 40 to a plasma treatment priorto the injection-molding procedure.

Mold cavity 54 is configured in such a way that the circumferential edgeof the blank is embedded in the plastic mass, and plastic layer 60produced by the injection molding (FIGS. 6 and 7) forms radiallyprojecting mounts 62 including fastening holes 64 at its edge, whichmake it possible to fix the cover in place on a radiator grille or someother body part of the motor vehicle (see also FIG. 8).

After plastic layer 60 has cooled in injection-molding machine 42, cover66 created by plastic layer 60 together with adhering blank 28 (FIGS. 7and 8) is demolded, and lower tool 16 is ejected as well with the aid ofejectors 46 and returned for further use to stamping and deep-drawingdevice 18.

Cover 66 may be used in the condition in which it leavesinjection-molding machine 42. However, in a further step using the sameor some other injection-molding machine, it is optionally possible toapply a filler layer to the front side (underside) of the blank by aninjection-molding step, similar to filler layer 68 illustrated in FIGS.6 and 7. As a minimum, this filler layer fills the depressions of therelief structure, but may form a continuous planar surface on the outerside of the cover; it is made of transparent plastic, such as atransparent polycarbonate, so that the relief structure remains visible.If needed, the planar surface of the filler layer is able to be coatedby scratch-proof transparent enamel.

FIG. 6 illustrates a further specific embodiment, in which filler layer68 is produced in a casting machine 70 with the aid of a simple castingtool 72 by the reaction-injection molding method (RIM). Low-viscositycasting compounds, such as on the basis of polyurethane or acrylate, maybe used for this purpose. An isocyanate and a polyol, for example, arecombined in a mixer head 74, and injected into the heated tool at apressure of less than 500 MPa. A cross-linked resin, which is verystable with regard to temperature and shape and which forms ascratch-proof planar surface that no longer needs to be enameled, isthen produced in the mold cavity by way of a chemical reaction.

Finished cover 66 obtained in such a manner is shown in a sectional viewin FIG. 7 and in a front view in FIG. 8.

1-15. (canceled)
 16. A method for producing a cover, the methodcomprising: reshaping a blank of flexible glass into a relief structure,wherein the blank forms a supporting substrate of the cover; wherein thecover is for a radar sensor for the motor vehicle, and includes a wallprovided with a three-dimensional relief structure, the wall having thethree-dimensional relief structure being made of deep-drawn glass. 17.The method of claim 16, wherein the relief structure is imprinted and/ormetallized on at least one side.
 18. The method of claim 16, wherein aplastic layer is applied on one side of the blank with the aid of theinjection-embossing method.
 19. The method of claim 16, wherein a fillerlayer from a transparent casting compound which cures by cross-linkingis formed on one side of the blank in the reaction-injection moldingmethod.
 20. The method of claim 16, wherein a filler layer from atransparent casting compound which cures by cross-linking is formed onone side of the blank, which is on a blank and non-metallized side, inthe reaction-injection molding method.
 21. The method of claim 16,wherein a plastic layer is applied on one side of the blank, which is onthe imprinted and/or metallized side, with the aid of theinjection-embossing method.